1. False. Disinfection inactivates various types of microorganisms, but some wastewater organisms are still present and viable after disinfection.

2. False. Many organic compounds from industrial dischargers will absorb ultraviolet light; even if all solids are removed, the transmittance still can be quite low (less than 30%).

3. True.

4. False. Chlorine was first used in London in 1850 after an outbreak of cholera.

5. True.

6. a.

7. c.

8. d.

9. a.

10. c. This ratio is based on stoichiometric relationships. The molecules react one to one, but their masses are different. The molecular weight of chlorine gas (Cl2) is 71 g; the molecular weight of sodium bisulfate (NaHSO3) is 104 g. So, 104 g of sodium bisulfate is needed for every 71 g of chlorine to be neutralized; 104 g ÷ 71 g = 1.46.